Signals: Fire, Smoke, and the Semaphore

Long before a wire carried a signal, nature did. Fire, smoke, and sound were all used to move a message faster than any human body could carry it. Information is power, and delivering a message quickly is the arbitrage that carries the value.

Key Milestones

• Fire and smoke, from roughly the 8th century BC in China onward. Beacon towers relayed warnings of invasion across vast distances, centuries before any writing system could travel that fast.
• Sound and sirens, from ancient warning horns to the electric siren in 1799. A single burst of sound could alert an entire village at once, useful exactly where fire and smoke could not be seen: at night, in fog, or through dense forest.
• Semaphore, 1792, the Chappe system in France. A relay of towers and telescopes turned mechanical arm positions into coded language, the direct conceptual ancestor of the electric telegraph.

The Energy, Social, and Economic Impact of Signals

The Chappe semaphore line from Paris to Lille, roughly 230 kilometers, could pass the first symbol of a message through 15 towers in just nine minutes, with a full message typically taking about 32 minutes. That works out to an effective signal speed of over 500 kilometers an hour, against a horse courier at roughly 10 kilometers an hour. It is worth pausing on that: in 1794, more than a century before the airplane, a message could already outrun anything on legs by fifty times, using nothing but wood, rope, and a telescope.

View chart in the full report

The homing pigeon from Part I's postlude sits in between: cruising at roughly 50 miles an hour, about 80 kilometers an hour, far slower than the semaphore's 500 but far faster than a horse. And unlike the semaphore, a pigeon needed no towers, no operators, and no government funding, just a bird that knew its way home. Speed was not the only currency in this arbitrage. Cost was too.